1. Field of the Invention:
This invention relates to a treatment for ripening of the cervix, particularly in the induction of labour to assist mammals to give birth or in connection with surgical or diagnostic procedure.
2. Description of the Related Art:
Parturition (expulsion of the fetus from the uterus), requires both contractions of the myometrium, the smooth muscle of the uterus, and a softening of the connective tissue of the cervix, so that it will stretch and dilate sufficiently to allow the fetus to be expelled. This softening is known as "ripening".
The current preferred method of cervical ripening is by the use of prostaglandin E.sub.2. This is used as a vaginal gel or tablet or as a gel placed in the cervix. One worry about the use of prostaglandin E.sub.2 is that there is a possibility of hyperstimulation of the uterus, leading to excessively strong myometrial contractions before the cervix is ripened and therefore before a comfortable or safe birth is possible. The ideal preparation would soften and efface the cervix without causing myometrial contractions. This would allow the subsequent contractions (induceable if necessary with a small dose of prostaglandin) to deliver the baby with a minimum of resistance. There is good evidence from animal experiments that the antiprogestins such as RU486 would meet these requirements, but the problem with this drug is that is has associated antiglucocorticoid activity which might be detrimental to the fetus.